Probably the easiest and most effective way to clean the carbon-encrusted grids and removable panels of your oven. Stick 'em in the bag, pour in the stuff, give it a wobble and leave for a few hours. They come out like new. I have no shame in telling you that our oven, although still a very good and functional oven is many years old and the inside grid shelves and panels were so manky that pretty-much shot blasting them looked like it was going to be the only way to really get them clean because scrubbing them and using other oven cleaning products just weren't working. My wife now proudly shows the neighbours the sparklingly clean inside of our twenty-four-year-old oven.
It's a Zannusi by the way, all it's ever had wrong with it has been a light bulb conking out. So if you're looking for an oven that'll still be there when the kids have grown up, get a Zannusi. It's now a 'new' oven coz it's very clean and it's got a new lightbulb.